Corticospinal output and cortical excitation-inhibition balance in distal hand muscle representations in nonprimary motor area

摘要: Transcranial magnetic stimulation (TMS) of the superior frontal gyrus in non-primary motor area (NPMA) can evoke motor-evoked potentials (MEPs) at 20 ms latency range contralateral distal hand muscles similar to M1 and indicating monosynaptic corticospinal tracts. We compared intracortical inhibitory excitatory balance primary cortex (M1) NPMA by navigated single- paired-pulse TMS (ppTMS). also evaluated spatial stability muscle representations remapping 11 healthy subjects one year after initial mapping. Resting threshold (rMT) was higher than as were MEP amplitudes evoked 120% rMT intensity local MT. Short-interval inhibition (SICI) significantly weaker ISI 2 conditioning stimulus (CS) 80% rMT. Our findings suggest that cortical 1) are connected lower motoneurons monosynaptically, 2) less strictly organized, i.e. motoneuron population representing a discrete is sparser dense 3) have capacity generate powerful, rapid contraction if sufficient number motoneurones activated. In NPMA, activity mainly M1. The SICI an may reflect strict topographic organization readiness reorganization neural circuits during learning or deficits. Hum Brain Mapp, 2010. © 2010 Wiley-Liss, Inc.